1. FIELD OF THE INVENTION
This invention relates generally to printers, and, more particularly, to a method and apparatus for controlling the movement of selected paper-holding trays which feed a printer, a copier, or the like.
2. DESCRIPTION OF THE RELATED ART
Printers, such as electrophotographic and laser printers, are typically used in an office environment where they are connected to personal computers, personal computer networks, or dedicated word processing computers. Most office printers, commonly referred to as desktop printers, share common advantageous characteristics. These characteristics include: small size, high print quality, quiet operation, and adequate speed for word processing applications.
These printers include paper handling mechanisms that usually employ separate trays for holding different types or different sizes of paper. These trays are typically configured to hold approximately 250 sheets of paper. If the paper handling mechanism includes only one tray, then the printer is capable of withdrawing paper from only the one tray during a requested printing operation. When the printer receives instructions to print on different types of paper during a printing operation, the single tray must be removed and replaced with another tray containing the proper paper.
To obviate this problem, printers have been adapted to include multiple trays from which different types or different sizes of paper may be withdrawn. When a multiple-tray printer receives instructions to print on different types of paper during a printing operation, the paper handling mechanism associated with the printer simply withdraws paper from the appropriate tray.
A paper-feeding mechanism is used to withdraw paper from a tray, and typically includes at least one rubber-like roller that rotatably engages the paper within the tray and draws the paper into the printing mechanism. When a printer includes a paper handling mechanism that includes more than one tray, each tray ordinarily has a dedicated paper-feeding mechanism associated with it. Further, the trays and their associated paper-feeding mechanisms are normally stacked in a vertical arrangement, and, therefore, consume vertical space equal to the vertical height of each 250 sheet tray and the vertical height of each paper-feeding mechanism. Accordingly, the combined vertical height of each tray and paper-feeding mechanism limits the maximum number of trays that can be associated with a paper handling mechanism of a desktop printer.
Commonly used paper trays include a spring that forces the paper within the tray into contact with the rubber-like roller of its associated paper-feeding mechanism. Since the paper-feeding mechanism is stationary, the spring force constantly maintains the top sheet of paper in contact with the paper-feeding mechanism so that the mechanism operates properly as the paper stack is depleted. However, when additional paper is loaded into a particular tray, the printing process from that tray must cease while the tray is removed and the paper supply replenished. This is particularly time consuming where the user wishes to print a short run of unique paper that differs from the paper currently loaded in any of the trays.
To obviate this problem, previous printers have employed a sheet feeding mechanism that allows an operator to print a small number of copies on a paper style unique from that currently loaded in any of the trays. The operator singularly and consecutively feeds the required number of sheets of the unique paper style into the sheet feeding mechanism. However, this is also a time consuming process that does not free the user to accomplish other tasks, but requires that the user remain at the printer, consecutively feeding each sheet of paper into the printer, until the entire printing process is complete.
Alternatively, the user may remove the tray from the paper handling mechanism, insert the desired number of sheets of paper into the tray, and replace the tray in the paper handling cassette. While this method does free the user to leave the printer during the printing process, the procedure of removing the tray and loading the tray with a precise number of unique sheets of paper causes the printer to discontinue printing until the tray has been replaced.
Since the market for desktop printers is highly competitive extremely cost sensitive, any proposed solution to these problems, or other advances in printer technology, should be economical, durable, and easy to manufacture and repair.
The present invention is directed to overcoming, or at least minimizing, one or more of the problems as set forth above.